1. Field of the Invention
The present invention relates to an image blur correction device and a camera, and more particularly relates to an image blur correction device that drives a correction lens and performs image blur correction, and to a camera equipped with this image blur correction device.
2. Description of the Related Art
Digital cameras that make use of image sensors such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) sensor to convert an optical image into an electrical signal, and record by digitizing the electrical signal, have become very popular in recent years. With these digital cameras, there is a need not only for increasing the number of pixels of the CCD or CMOS sensor, but also for improving the performance of the lens barrel that forms the optical image on these image sensors. More specifically, there is a need for a lens barrel equipped with a high-power zoom lens system.
Meanwhile, the housing of digital cameras needs to be made more compact in order to make these products more portable. To this end, there is a need for reduced size in an image pickup apparatus equipped with a lens barrel and image sensors, which is believed to contribute greatly to reducing the size of the housing. In these efforts to reduce the size of an image pickup apparatus, what is known as a folding optical system has been proposed, in which the apparatus is reduced in size by bending the zoom lens system at some point along the optical path, without changing the optical length.
For instance, Japanese published unexamined application JPH11-258678 discloses a folding optical system that uses a reflecting mirror to bend the optical path. More specifically, the lens barrel disclosed in JPH11-258678 is equipped with a first lens group and a second lens group, in that order from the subject side, on the subject side of the reflecting mirror, and is equipped with a third lens group and a fourth lens group, in that order from the reflecting mirror side, on the image sensor side of the reflecting mirror. The first lens group is fixed. The second and third lens groups are each movable in the optical axial direction, and a zoom lens system is constituted by the co-movement of these. The fourth lens group is used for focus adjustment.
Japanese published unexamined application JP2003-169236 discloses a folding optical system that uses a prism to bend the optical path. More specifically, the lens barrel disclosed in JP2003-169236 is equipped with a lens group on the subject side of the prism. The lens group is movable in the optical axial direction between a usage position and a storage position. The prism is also movable, so as to ensure enough room for the lens group when the lens group is in its storage position.
Japanese published unexamined application JP2004-102089 discloses a constitution of a lens group used in a folding optical system.
However, further improvement is necessary before the need for a higher-power zoom lens system and the need for a smaller size can both be realized at the same time.
More specifically, with the constitutions disclosed in JPH11-258678 and JP2003-169236 it is difficult to achieve a smaller apparatus size while at the same time configuring a high-power zoom lens system. Furthermore, even if the lens configuration disclosed in JP2004-102089 is employed, no constitution for reducing the apparatus size is disclosed, and the specific apparatus constitution is not clear.
Meanwhile, in general, when an image pickup apparatus is reduced in size, or is equipped with a high-power zoom lens system, there is a need to prevent blur of the captured image, the main cause of which is camera shake.
FIG. 20 is an exploded perspective view of an image blur correction device in an example of prior art (see Japanese published unexamined application JP2000-75338). With the image blur correction device shown in FIG. 20, a second lens group 101 is supported by a lens frame 102, and the lens frame 102 is movably supported by a guide shaft 103 that guides movement in the pitching and yawing directions. Also, the lens frame 102 is provided with coils 104a and 104b for driving the lens frame 102 in the pitching and yawing directions. Magnets 106a and 106b are provided to a stationary base 105, across from the coils 104a and 104b, respectively. When power is sent to the coils 104a and 104b, driving force is generated in the pitching and yawing directions, and the second lens group 101 is driven in each of these directions. The amount of blur of the lens barrel is detected by angular velocity sensors 107a and 107b, power is sent to the coils 104a and 104b according to the detection signal, and image blur is corrected.
The need for reduced size is still present even with an image pickup apparatus in which an image blur correction device is mounted. To meet this need, with conventional image blur correction device installed in an image pickup apparatus, there have been attempts at reducing the size in the optical axial direction of the light incident on the image blur correction device.
Meanwhile, it has become necessary to mount image blur correction device in various kinds of image pickup apparatus. In this case, to afford greater latitude in the design of the image pickup apparatus, not only does the size of the image blur correction device need to be reduced in the optical axial-direction, but the size in any direction perpendicularly intersecting the optical axis also needs to be reduced. For example, when the above-mentioned image blur correction device is installed in an image pickup apparatus having a folding optical system, if a conventional image blur correction device is installed on the side of the reflecting mirror or prism from which light exits, then the size of the image pickup apparatus increases in a direction perpendicular to the optical axis of the light incident on the image blur correction device. Specifically, the size (thickness) of the image pickup apparatus in the optical axial direction of the light incident on the reflecting mirror or prism increases. This is because with a conventional image blur correction device, two drive units for driving the correction lens (used to correct image blur) in the pitching and yawing directions are disposed 90 degrees apart and centering around the correction lens.
Also, as discussed above, with a conventional image blur correction device, the guide shaft 103 is provided so that the pitching movement frame and yawing movement frame can advance in the pitching and yawing directions. Accordingly, space is required for the installation of the guide shaft 103, and this makes it more difficult to reduce the size of the image blur correction device.
Also, reducing the size in any direction of an image pickup apparatus by installing an image blur correction device whose size has been reduced in any direction perpendicularly intersecting the optical axis is a way of increasing the consumer appeal of an image pickup apparatus, and not just an image pickup apparatus having a folding optical system.
In view of this, to further reduce the size of an image blur correction device, an image blur correction device has been proposed in which the correction lens is rotationally driven around a rotational axis disposed substantially parallel to the optical axis of the correction lens (see Japanese published unexamined application H7-5514 (FIGS. 6 and 8), for example). FIGS. 21 and 22 are exploded perspective views of an image blur correction device in an example of prior art.
The image blur correction device shown in FIG. 21 is mainly constituted by a support frame 15 to which a correction lens 16 is fixed, a support arm 13 that supports the support frame 15 so that it is capable of linear motion, and a barrel 11 that supports the support arm 13 to be rotatable. With this image blur correction device, the support arm 13 is rotationally driven along an arc whose center is a shaft 45a with respect to the barrel 11, by a coil 46a attached to the barrel 11 and a permanent magnet 45 attached to the support arm 13. The support frame 15 is driven in a direction perpendicularly intersecting the optical axis with respect to the support arm 13, by permanent magnets 47a and 47b attached to the support frame 15 and a coil 49 attached to the support arm 13. With this constitution, a correction lens 16 is movable in the pitching and yawing directions within a plane perpendicularly intersecting the optical axis.
The image blur correction device shown in FIG. 22 is mainly constituted by a support frame 15 to which a correction lens 16 is fixed, a support arm 13 that supports the support frame 15 to be rotatable and a barrel 11 that supports the support arm 13 so that it is capable of linear motion. With this image blur correction device, the support arm 13 is driven in a direction perpendicularly intersecting the optical axis with respect to the barrel 11, by a permanent magnet 63y attached to the barrel 11 and a coil 62y attached to the support arm 13. The support frame 15 is driven in a direction perpendicularly intersecting the optical axis with respect to the support arm 13, by a coil 62p attached to the support frame 15 and a permanent magnet 63p attached to the support arm 13. With this constitution, the correction lens 16 is movable in the pitching and yawing directions within a plane perpendicularly intersecting the optical axis.
With the image blur correction device shown in FIGS. 21 and 22, one support frame is driven along an arc whose center is the rotational axis. Accordingly, friction is reduced during drive of the support frame, and the drive unit having a coil and a permanent magnet can be smaller. Compared to the image blur correction device described in JPH11-258678, JP2003-169236, JP2004-102089, and JP2000-75338 above, one less guide shaft for linearly moving is needed. This allows the guide mechanism to be smaller. That is, the image blur correction device shown in FIGS. 21 and 22 allow a further reduction in size.
However, with the image blur correction device shown in FIGS. 21 and 22, there is the risk of a decrease in image blur correction performance. More specifically, with the image blur correction device shown in FIG. 21, the driving force for rotating the correction lens 16 acts on the support arm 13, but does not act directly on the support frame 15 to which the correction lens 16 is fixed. With the image blur correction device shown in FIG. 22, the driving force for linearly moving the correction lens 16 acts on the support arm 13, but does not act directly on the support frame 15 to which the correction lens 16 is fixed. Consequently, the lens support member may not be supported in the desired position, depending on the dimensional accuracy of the portion where the support arm 13 and the support frame 15 are linked. This poses the risk of a decrease in the positional accuracy of the correction lens.
Thus, when size is reduced, there is the risk of a decrease in the image blur correction performance.
Also, with the image blur correction device described in JPH11-258678, JP2003-169236, JP2004-102089, and JP2000-75338, the guide shaft is fixed adhesively, for example. Consequently, the manufacture of the image blur correction device entails the work of applying and drying an adhesive agent. As a result, the manufacture becomes more complicated, and this drives up the manufacturing cost.